Elongated connecting elements, such as rods, plates, tethers, wires, cables, and other devices have been implanted along the spinal column and connected between two or more bone anchors engaged between one or more spinal motion segments. Such connecting elements can be positioned in the respective bone anchors with a top-down approach, a side-to-side approach, or a serial, endwise approach. In any event, it is desirable to securely engage the connecting element in the bone anchor to maintain the spinal stabilization effect provided by the connecting element when engaged between the bone anchors.
Set screws, nuts, caps, and other engaging members can be engaged to the bone anchor to maintain the connecting element therein. However, it can be desirable to enhance the engagement relationship between the engaging member and connecting element to prevent or resist movement of the connecting element relative to the bone anchor. In addition, enhancement of the engagement of the engaging member with the connecting element can prevent the engaging member from “backing out” or loosening from the bone anchor after engagement thereto.